This wireless doorbell has a built-in signal generator and door sensor. The kit includes two transmitters and one receiver. When a transmitter is activated, the receiver receives the signal. The combination of the built-in signal generator and door sensor provides a compact and efficient notification solution. All necessary accessories are included in the package for immediate use. The two transmitters can receive signals from different doors or entrances. The receiver ensures that messages are delivered clearly to your device. This system is suitable for homes or offices that need to monitor multiple entrances. The product description lists the items you will receive: a wireless doorbell with built-in signal generator and door sensor, two transmitters, and one receiver. This is a complete solution that can be easily integrated into existing security or notification systems.